A parallel implementation of the conventionally used NDDO (MNDO, AM1, PM3, CLUSTER-Z1) and modified NDDO-WF (CLUSTER-Z2) techniques for semiempirical quantum chemical calculations of large molecular systems in the sp- and spd-basis, respectively, is described. The atom-pair distribution of data over processors forms the basis of the parallelization. The technological aspects of designing scalable parallel calculations on supercomputers (using ScaLAPACK and MPI libraries) are discussed. The scaling of individual algorithms and the entire package was carried out for model systems with 894, 1920, and 2014 atomic orbitals. The package speed-up provided by different multiprocessor systems involving a cluster of Intel PIII processors, Alpha-21264-processor-built machine MBC-1000M, and Cray-T3E is analyzed. The effect of computer characteristics on the package performance is discussed. © 2002 Wiley Periodicals, Inc. Int. J. Quantum Chem.